What is Constants in VB.net?
The VB.net Constants are fixed values that the program cannot change while it is running. Literals are another name for these fixed values. Integer constants, floating constants, character constants, and string literals are all examples of basic data types. Enumeration constants are also present.
Constants in VB.net are processed similarly to ordinary variables, with the exception that their values cannot be changed after they have been defined. These constants can be of any data type, such as Integer, Double, String, Decimal, Single, character, enum, etc.
An enumeration is a set of named integer constants.
Constants in VB.net : Table of contents
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VB.net Constant Declaration
Constants in VB.net are declared using the Const statement. The Const statement is used at module, class, structure, procedure, or block level for use in place of literal values.
The syntax for the Const statement is:
'syntax for the const' [ < attributelist > ] [ accessmodifier ] [ Shadows ] Const constantlist
1. Attributelist
Attributelist − specifies the list of attributes applied to the constants; you can provide multiple attributes separated by commas. Optional.
2. Accessmodifier
Accessmodifier − specifies which code can access these constants. Optional. Values can be either of the: Public, Protected, Friend, Protected Friend, or Private.
3. Shadows
Shadows − this makes the constant hide a programming element of identical name in a base class. Optional.
4. Constantlist
Constantlist − gives the list of names of constants declared. Required.
each constant name has the following syntax and parts:
'constants name syntax' constantname [ As datatype ] = initializer
1. constantname
constantname − specifies the name of the constant
2. datatype
datatype − specifies the data type of the constant
3. initializer
initializer − specifies the value assigned to the constant
For Example:
'The following statements declare constants.' Const maxval As Long = 4999 Public Const message As String = "HELLO ITSOURCECODERS" Private Const piValue As Double = 3.1415
Example Code of Constants Value
The following example demonstrates declaration and use of a constant value
'Example Code of Constants Value' Module constantsNenum Sub Main() Const PI = 3.14149 Dim radius, area As Single radius = 7 area = PI * radius * radius Console.WriteLine("Area = " & Str(area)) Console.ReadKey() End Sub End Module
When the above code is compiled and executed, it produces the following result:
Area = 153.933
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Print and Display Constants in VB.net
VB.net provides the following print and display constants in VB.net
Sr.No. | Constant & Description in VB.net |
---|---|
1. | vbCrLf Carriage return/linefeed character combination. |
2. | vbCr Carriage return character. |
3. | vbLf Linefeed character. |
4. | vbNewLine Newline character. |
5. | vbNullChar Null character. |
6. | vbNullString Not the same as a zero-length string (“”); used for calling external procedures. |
7. | vbObjectError Error number. User-defined error numbers should be greater than this value. For example: Err.Raise(Number) = vbObjectError + 1000 |
8. | vbTab Tab character. |
9. | vbBack Backspace character. |
Declaring Enumerations in VB.net
An enumerated type is declared using the Enum statement. The Enum statement declares an enumeration and defines the values of its members. The Enum statement can be used at the module, class, structure, procedure, or block level.
The syntax for the Enum statement is as follows:
'syntax for enum statement' [ < attributelist > ] [ accessmodifier ] [ Shadows ] Enum enumerationname [ As datatype ] memberlist End Enum
1. attributelist
attributelist − refers to the list of attributes applied to the variable. Optional.
2. accessmodifier
accessmodifier − specifies which code can access these enumerations. Optional. Values can be either of the: Public, Protected, Friend or Private.
3. Shadows
Shadows − this makes the enumeration hide a programming element of identical name in a base class. Optional.
4. enumerationname
enumerationname − name of the enumeration. Required
5. datatype
datatype − specifies the data type of the enumeration and all its members.
6. memberlist
memberlist − specifies the list of member constants being declared in this statement. Required.
Each member in the memberlist has the following syntax and parts:
1. name
name − specifies the name of the member. Required.
2. initializer
initializer − value assigned to the enumeration member. Optional.
For Example:
'Example of Memberlist' Enum Colors red = 1 orange = 2 yellow = 3 green = 4 azure = 5 blue = 6 violet = 7 End Enum
Example Code for Declaration and Use of The Enum Variable Colors
The following example demonstrates declaration and use of the Enum variable Colors
'Example Code for Declaration and Use of The Enum Variable Colors' Module constantsNenum Enum Colors red = 1 orange = 2 yellow = 3 green = 4 azure = 5 blue = 6 violet = 7 End Enum Sub Main() Console.WriteLine("The Color Red is : " & Colors.red) Console.WriteLine("The Color Yellow is : " & Colors.yellow) Console.WriteLine("The Color Blue is : " & Colors.blue) Console.WriteLine("The Color Green is : " & Colors.green) Console.ReadKey() End Sub End Module
When the above code is compiled and executed, it produces the following result:
The Color Red is : 1
The Color Yellow is : 3
The Color Blue is : 6
The Color Green is : 4
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Summary
Const values help clear up confusing code. They influence performance often in a positive way. With Const we construct self-documenting code. A Const with the identifier “name” is known to be a name by any programmer reading the code.